This invention relates to electrophotographic developing arrangements in which an electrostatic image is developed by a liquid developer.
Conventional electrophotographic liquid developing arrangements bring a liquid developer into contact with an electrostatic image to be developed in any of several different ways. According to one method, the surface of a photoreceptor or other member carrying an electrostatic image is merely dipped into a bath of liquid developer to develop the electrostatic image. In another method, such as described in U.S. Pat. No. 5,017,968, for example, liquid developer is supplied to a head which extends across the width of a member bearing an electrostatic image and liquid developer is supplied through one channel in the head to a slot opening where it is brought into contact with the surface of the electrostatic image-bearing member. The liquid developer is then withdrawn from the slot opening through another channel in the developing head. In a further liquid development arrangement, as shown in U.S. Pat. No. 5,708,937, for example, a rotating cylinder is coated with liquid developer at a supply point and carries the developer into contact with the electrostatic image-bearing member to develop the image. Other arrangements for supplying liquid developer to an image-bearing member through a slot extending across the width of the member are disclosed in U.S. Pat. Nos. 5,708,936, 5,737,672 and 5,765,078.
Such arrangements for supplying liquid developer to an electrostatic image-bearing member have certain disadvantages including generation of odors resulting from vaporization of developer liquid within the region of the developing unit, difficulties in reproducing colored images with successive developers of different color in a single pass of the image-bearing member, and excessive size and cost of the developing units.
U.S. Pat. Nos. 5,358,659, 5,567,564 and 5,667,716 disclose methods of preparing magnetic liquid developers while U.S. Pat. No. 4,797,013 discloses the use of ferrofluids retained by magnets in gaps between moving members to seal lubricants in bearing arrangements and U.S. Pat. No. 4,645,960 discloses a ferrofluid bearing.
U.S. Pat. No. 5,461,466 discloses a dripless seal for a liquid toner cartridge by which the cartridge is closed when not in use.